Magnetic-pole detecting system for synchronous AC motor and magnetic-pole detecting method therefor

Abstract

A magnetic-pole detecting system for synchronous AC motors and a magnetic-pole detecting method therefor are provided. The magnetic-pole detecting system for synchronous AC motors includes a position detector 10 for detecting the relative position between the moving element 3 and the stator of an AC motor 5; a phase-update command unit 52 for making a plurality of currents with different phases flow in coils 3a and 3b so that the moving element 3 moves to a plurality of stable points; a reversal command unit 56 for making currents flow in the coils 3a and 3b so that the moving element 3 reverses from the previous direction in which the moving element 3 has been moved by the phase-update command unit 52; a current cut-off command unit 54 for cutting off the currents flowing in the coils 3a and 3b when the position-detector 10 detects a movement of the moving element 3; a reversal-determining unit 64 for determining, based on a position-detecting signal from the position-detector 10, a direction in which the moving element has moved based on the phase-update command unit 52, and for determining that the determined direction has reversed between the previous and the present instances; and a stable-point-simulator for simulating a stable point by means of the phase of the currents flowing in the moving element 3 when the reversal-determining unit 64 has detected the reversal.

Description

TECHNICAL FIELD[0001]This invention relates to magnetic-pole detecting systems for synchronous AC motors (referred to as a magnetic-pole detecting system, hereinafter) and magnetic-pole detecting methods therefor, and more particularly, to improvement in initial magnetic-pole detection.BACKGROUND ART[0002]In a synchronous AC motor, magnetic-pole position needs to be detected in order to determine the phase of the current that flows in each phase coil. For this purpose, magnetic-pole detecting systems in which magnetic-pole position is detected by making each phase current flow in a certain pattern so that the moving element moves to a corresponding stable point are known.[0003]A conventional magnetic-pole detecting system as mentioned above will be described referring to Japanese Laid-Open Patent Publication 1991-89886. According to the patent publication, a magnetic-pole detecting system detects initial magnetic-pole position by changing the phases of an α-phase current Iα and a β-...

AI Technical Summary

Benefits of technology

The present invention provides a simplified magnet-pole detecting system and method that does not require feedback of position, speed, and the like. The system includes a synchronous AC motor with phase coils, a position-detecting means, a movement-determining means, a current cut-off means, a reversal-determining means, and a stable-point simulating means. The method includes sequentially generating currents with different phases, cutting off the currents when the movement-detecting means detects movement, and simulating the position of the moving element based on the phase of the first current command signal when the reversal-determining means detects a reversal. The technical effect is that no moving-element oscillation occurs when the moving element is made to move to a stable point, and the travel distance of the moving element is shortened.

Problems solved by technology

However, in the conventional magnet-pole detecting system, in order to inhibit the oscillation of the moving element, a speed detector for detecting the travel speed of the moving element and a phase compensator for compensating the current phases in correspondence with the travel speed of the moving element must be provided, and furthermore the speed feedback value of the moving element has to be adjusted, and thus there has been a problem in that the magnetic-pole detecting system is complex.

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